[USRP-users] rx_samples_to_file issue

gsmandvoip gsmandvoip at gmail.com
Thu Oct 2 23:48:25 EDT 2014


Thanks Marcus for your replies. Yes O gone away.

On Thu, Oct 2, 2014 at 5:50 PM, Marcus D. Leech <mleech at ripnet.com> wrote:

>   with  rx_samples_to_file without _4rx.rbf, Initially I tried on my i3,
> 4GB ram, it gave me
> some OOOO but was lesser than earlier, but I do not understand, my most of
> the ram capacity and processor was sitting idle while it shows OOOO, why is
> this strange behaviour
>
> The default format for uhd_rx_cfile is complex-float, thus doubling the
> amount of data written compared to rx_samples_to_file.
>
> You can't just use CPU usage as an indicator of loading--if you're writing
> to disk, the disk subsystem may be much slower than you think, so the
>   "rate limiting step" is writes to the disk, not computational elements.
>
> Try using /dev/null as the file that you write to.  If the 'O' go away,
> even at higher sampling rates, then it's your disk subsystem.
>
>
>  using uhd_rx_cfile getting similar result, but strangely, why it is low,
> at 4M sampling rate it was higher???
>
>
> On Thu, Oct 2, 2014 at 9:27 AM, Marcus D. Leech <mleech at ripnet.com> wrote:
>
>>  On 10/01/2014 11:46 PM, gsmandvoip wrote:
>>
>>  Yes I am running single channel, but when trying to achieve my desired
>> sampling rate without _4rx.rbf, it says, requested sampling rate is not
>> valid, adjusting to some 3.9M or so.
>>  sorry for misleading info I gave earlier, I have i3, with 32 bit and i7
>> with 64 bit, but getting same result on both machines
>>
>>  Here is my command to capture signal:
>>
>> ./rx_samples_to_file --args="fpga=usrp1_fpga_4rx.rbf, subdev=DBSRX"
>> --freq "$FC" --rate="$SR" $FILE --nsamps "$NSAMPLES"
>>
>> and here is its output:
>>
>> Creating the usrp device with: fpga=usrp1_fpga_4rx.rbf, subdev=DBSRX...
>> -- Loading firmware image: /usr/share/uhd/images/usrp1_fw.ihx... done
>> -- Opening a USRP1 device...
>> -- Loading FPGA image: /usr/share/uhd/images/usrp1_fpga_4rx.rbf... done
>> -- Using FPGA clock rate of 52.000000MHz...
>> *Error: LookupError: IndexError: multi_usrp::get_tx_subdev_spec(0) failed
>> to make default spec - ValueError: The subdevice specification "A:0" is too
>> long.*
>> The user specified 1 channels, but there are only 0 tx dsps on mboard 0.
>>
>>
>>   Don't use the _4rx image if you don't need it.
>>
>> The USRP1 only does strict-integer resampling, and with a master clock
>> (NON STANDARD FOR USRP1) of 52.000MHz, 4Msps is not a sample rate
>>   that it can produce.   Try 5.2Msps or 4.3333Msps.
>>
>> At 5.2Msps, it's recording at roughly 20.8Mbytes/second, so your system
>> needs to be able to sustain that for at least as long as the capture lasts.
>>
>>
>>
>
>
> --
> Marcus Leech
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortiumhttp://www.sbrac.org
>
>
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